Chapter 20, Problem 1P

Choose the best matching phrase in the right column for each of the terms in the left column.

a. fitness	1. the genotype with the highest fitness is the heterozygote
b. gene pool	2. chance fluctuations in allele frequency
c. fitness cost	3. mutations accumulate at a relatively constant rate
d. allele frequencies	4. p = 1.0
e. heterozygote advantage	5. ability to survive and reproduce
f. equilibrium frequency	6. p and q
g. genetic drift	7. event that drastically lowers N
h. molecular clock	8. the advantage of a particular genotype in one situation is a disadvantage in another situation
i. population bottleneck	9. frequency of an allele at which q = 0
j. hominins	10. collection of alleles carried by all members of a population
k. fixation	11. Homo sapiens, Neanderthals, and Denisovans

Summary Introduction

a.

To determine:

The phrase that describes “fitness” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Fitness in the field of genetics can be described as a term that means ability of an organism to survive and produce offsprings.

Answer to Problem 1P

Correct answer:

Fitness: Ability to survive and reproduce

Explanation of Solution

Fitness is defined as the ability of an organism to survive and reproduce efficiently. It is the ability of an organism to successfully transmit its genetic material (genes) to the next generation.

Thus, the term that describes “ability to survive and reproduce” is fitness.

Summary Introduction

b.

To determine:

The phrase that describes “gene pool” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Gene pool refer to the collection of alleles or genes that are usually present in an interbreeding population.

Answer to Problem 1P

Correct answer:

Gene pool: Collection of alleles carried by all members of a population

Explanation of Solution

The collection of all the genes or alleles that are found in a particular population is termed as the gene pool. It is an important concept of population genetics as it helps in determining all the alleles that are common in a population.

Thus, the term that describes “the collection of alleles carried by all the members of a population” is the gene pool.

Summary Introduction

c.

To determine:

The phrase that describes “fitness cost” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Fitness cost in terms of genetics is related to the selective advantage provided to a geneotype in one condition, but it may be disadvantageous in other conditions.

Answer to Problem 1P

Correct answer:

Fitness cost: The advantage of a particular genotype in one situation is a disadvantage in another situation

Explanation of Solution

Fitness cost is defined as the process by which the advantage of a genotype in one condition turns out to be a disadvantage in another situation. For example, “RR” is the genotype that codes for insecticide resistance. The frequency of this genotype increases in the presence of an insecticide while its frequency reduces in the absence of an insecticide.

Thus, the term that describes “the advantage of a particular genotype in one situation is a disadvantage in another situation” is fitness cost.

Summary Introduction

d.

To determine:

The phrase that describes “allele frequencies” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Allele frequencies can be associated with gene frequencies and can be used to calculate genotype frequencies with the help of Hardy-Weinberg equilibrium.

Answer to Problem 1P

Correct answer:

Allele frequencies: p and q

Explanation of Solution

The proportion of gene copies that are of a common allele type in a population is termed as allele frequency. Geoffrey H. Hardy was a scientist who proposed the concept of Hardy-Weinberg equilibrium. This concept is used to associate the allele frequency with the genotype frequency.

According to Hardy-Weinberg equilibrium:

$p+q=1$

where:

p and q are the allele frequencies.

Thus, the p and q are allele frequencies.

Summary Introduction

e.

To determine:

The phrase that describes “heterozygote advantage” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Heterozygote advantage is related to the fitness level of heterozygous genotype.

Answer to Problem 1P

Correct answer:

Heterozygote advantage: The genotype with the highest fitness is the heterozygote

Explanation of Solution

There are two types of organisms. These are heterozygotes and homozygotes. The organism that has the same type of alleles for a particular genotype is termed as a homozygote. However, the organism that contains different alleles for genotypes is termed as heterozygotes. This type of organism produces different types of offsprings. Heterozygote advantage is used to indicate that the genotype that has the highest fitness is a heterozygote and not a homozygote.

Thus, the term that describes that a hetrozygote has the highest fitness is hetrozygote advantage.

Summary Introduction

f.

To determine:

The phrase that describes “equilibrium frequencies” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Equilibrium frequency refers to the frequency at which Δq is found to be zero.

Answer to Problem 1P

Correct answer:

Equilibrium frequency: Frequency of an allele at which Δq = 0

Explanation of Solution

The allele frequency is represented as “p and q”. Equilibrium frequency is defined as the allele frequency when Δq = 0. This is because the frequency of an allele is at equilibrium when q is equal to 0.

Thus, the equilibrium frequency is the frequency on allele when Δq = 0.

Summary Introduction

g.

To determine:

The phrase that describes “genetic drift” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Genetic drift refers to random changes of a frequency of an allele over a period of time in a population.

Answer to Problem 1P

Correct answer:

Genetic drift: Chance fluctuations in allele frequency

Explanation of Solution

The proportion of gene copies that are of a common allele type in a population is termed as allele frequency. Genetic drift is defined as the random changes in the allele frequency. The changes that are responsible for genetic drift are results of random inheritance. Thus, the term that describes chance fluctuations in the allele frequency is genetic drift.

Summary Introduction

h.

To determine:

The phrase that describes “molecular clock” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

The molecular clock plays a significant role in different areas of evolutionary biology.

Answer to Problem 1P

Correct answer:

Molecular clock: Mutations accumulate at a relatively constant rate

Explanation of Solution

An organism which is closely related has a high degree of the arrangement whereas; distantly reacted species has dissimilar arrangements. The scientists use a technique called the molecular clock. The molecular clock is used to detect the time period when organisms diverged from a common ancestor.

Thus, the term that describes the accumulation of mutation at constant rate is molecular clock.

Summary Introduction

i.

To determine:

The phrase that describes “population bottleneck” among the options given below.

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Reduction in the size of population due to environmental problems and anthropogenic activities is called population bottleneck.

Answer to Problem 1P

Correct answer:

Population bottleneck: Event that drastically lowers N

Explanation of Solution

The phenomenon by which a large population perishes randomly is termed as a population bottleneck. These are the events that rapidly lower the frequency of a population (N).

Thus, the event that drastically lowers N is called population bottleneck.

Summary Introduction

j.

To determine:

The phrase that describes “hominins” among the options given below:

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans.

Introduction:

Hominin consists of Homo sapiens, Neanderthals, and Denisovans.

Answer to Problem 1P

Correct answer:

Hominins: Homo sapiens, Neanderthals, and Denisovans.

Explanation of Solution

Hominin is a taxonomic tribe that is composed of Homo sapiens, Neanderthals, and Denisovans. It has been observed that the modern human of Europe mate with the hominins.

Thus, the term that describes “Homo sapiens, Neanderthals, and Denisovans” is hominins.

Summary Introduction

k.

The phrase that describes “fixation” among the options given below:

1. the genotype with the highest fitness is the heterozygote

2. chance fluctuations in allele frequency

3. mutations accumulate at a relatively constant rate

4. p = 1.0

5. ability to survive and reproduce

6. p and q

7. event that drastically lowers N

8. the advantage of a particular genotype in one situation is a disadvantage in another situation

9. frequency of an allele at which Δq = 0

10. collection of alleles carried by all members of a population.

11. Homo sapiens, Neanderthals, and Denisovans

Introduction:

Fixation is achieved when the frequency of specific gene has reached 100% in a population.

Answer to Problem 1P

Correct answer:

Fixation: p = 1.0

Explanation of Solution

The scientists consider a population to be fixed when a single allele is able to survive in all the individuals. It is the state at which any change after fixation cannot take place. The allele frequency (p and q) is 1.0 when fixation occurs.

Thus, the term that describes “p = 1.0” is fixation.